Sectional hydraulic valves are commonly used on truck mounted forklifts and other load handling vehicles where a hydraulic pump is used to deliver hydraulic fluid to a plurality of hydraulic cylinders. The sectional hydraulic valve may be configured to deliver the hydraulic fluid to two or more of the plurality of cylinders simultaneously and indeed may be configured to prioritize the supply of hydraulic fluid to one or more of the cylinders. European Patent Application Publication No. EP1,471,263, in the name of Kobelco Construction Machinery Co., Ltd, discloses a hydraulic valve device and method of assembling the same.
Sectional hydraulic valves are particularly effective in truck mounted forklifts as the valves are relatively compact and relatively lightweight compared with alternative arrangements, both of which are very important considerations in the design of any component for a truck mounted forklift. Furthermore, the truck mounted forklifts often require simultaneous operation of several hydraulic cylinders at once and the sectional hydraulic valves provide a relatively simple and straightforward solution to the problem of distributing the hydraulic fluid to each of the cylinders while ensuring safe and smooth operation of the truck mounted forklift.
In recent years, truck mounted forklift manufacturers have developed remote control systems to allow limited operation of their forklift machines without an operator in the driver's station. These systems are deemed advantageous from a health and safety point of view as the operator may now mount and dismount the forklift from the rear of a carrying vehicle without having to board or alight from the forklift when the forklift is at height on the rear of a carrying vehicle. This obviates the possibility of the operator falling from height before, during or after the mounting or dismounting operation.
There are however problems with the remote control systems that allow limited operation of the forklift machines and more specifically the hydraulic configurations used with these remote control systems. First of all, additional valves and hoses are required and in some systems an electric motor pump separate from the main engine driven hydraulic pump are needed to pressurise the hydraulic fluid to operate the cylinders in remote control mode. The pump and valves are expensive and add weight to the truck mounted forklift. More importantly though, the hydraulic fluid pressurised by these valves and pump must be fed to the hydraulic lines of the cylinders and this requires an external connection into the hydraulic lines from the sectional hydraulic valve and a number of other connections between the additional valves and electric motor and pump. Each of these connections introduces a potential leak point for hydraulic fluid which is highly disadvantageous.
In addition to the foregoing, the hydraulic piping and connections required for the remote control system add weight and take up a substantial amount of space on the truck mounted forklift which is also highly disadvantageous due to the compact nature of these machines. Generally speaking, the additional hydraulic piping and connections are tightly packed into the limited available space on the forklift truck making construction and repair of these components difficult and time consuming.
It is an object of the present invention to provide a sectional hydraulic valve that overcomes at least some of these problems and provides a useful choice to the consumer. It is a further object of the present invention to provide a truck mounted forklift that overcomes at least some of these problems and provides a useful choice to the consumer.